1. Field of the Invention
This invention relates to techniques for making hydrotreating catalysts from sepiolite. This invention further relates to processes for hydrotreating or selectively demetallizing hydrocarbons and the hydroprocessing of heavy oils.
2. Description of the Prior Art
The presence of impurities such as sulfur, nitrogen and metals in the hydrocarbon feedstocks now utilized in the manufacture of hydrocarbon fuels such as gasoline and diesel fuel is becoming increasingly important. These feedstocks include crude oils, heavy oils, cracked oils, deasphalted oils, residual oils, vacuum gas oils, vacuum residue, oil from tar sands, shale and mixtures thereof. Sulfur, nitrogen and metal impurities are discharged into the atmosphere, together with the exhaust gas when these hydrocarbons are burned and are thus an increasing source of environmental pollution. The metals present in the feedstocks are deposited on catalysts utilized in the catalytic cracking and/or hydroprocessing of hydrocarbons. These deposits cause a marked decrease in the catalytic activity of the catalysts and their selectivity. U.S. Pat. Nos. 4,152,250 and 4,196,102 describe the demetallization of hydrocarbon feedstocks as well as their denitrification and desulfurization utilizing a catalyst which comprises one or more metals selected from the group consisting of transition metals and metals of Group IIb of the periodic table supported on sepiolite carrier. U.S. Pat. No. 4,196,102 discloses a catalyst comprising one or more metals selected from the group consisting of transition metals and metals of Group IIb of the Periodic Table supported on a sepiolite carrier to be useful in the demetallization of hydrocarbons. We have now discovered that, in sepiolite-based catalysts, the residual acidity (both the indiginous acidity and that created in the catalyst preparation steps) can be controlled if the exchanged catalyst is subsequently ion-exchanged with magnesium ions. The catalyst is further improved by incorporating with it, after the magnesium ion-exchange, a high silica/alumina ratio zeolite to obtain the desired type of acidity at the desired level.